I've gotten to the point that I WILL NOT answer any call from a number I don't recognize. I have No-Mo-Robo set up for my home phone (Vonage) and it works really well!
I've noticed a much higher volume of "spam" calls coming in on my cell phone the last 6-10 months or so, but again I don't answer ANY number I don't recognize and send it directly to voicemail. Quite a few of them have the same area code and prefix as my number. Quite often I will see the number on my cell phone, I send it to voicemail and block the number. I will then dial that number from my office phone (which is often blocked). It rings and I get "boop-boop-beep... the number you dialed is not in service...."
IF the caller leaves a message, I know it's a real call and will unblock the number after listening to the message.
<span style="text-decoration: underline;">The latest scam</span>: In the last week or so I've been getting spam text messages (1 to 3 per day) from a number that looks like my service provider, a 5 digit number like "986-57". The messages have been something like "Hi Jaime, I have this great job for you, if you're interested click here: (some BS web link), test STOP if you're not interested".... or variations of that. I simply BLOCK that number and delete the message. If you click the link, who knows what sort of virus may upload into your phone. IF I click "stop" I'm SURE it will start a barrage of new spam messages being sent. So a word to the wise: do nothing other than delete the message.